This invention relates to a method for producing high-strength steel strip having exceptional formability and a ferrite-martensite, dual-phase structure.
The demand for easily formable, high-strength steel strip has increased steadily in recent times, most notably in the automotive industry where structural safety considerations have had to be reconciled with production requirements.
In an effort to meet this demand, a variety of steels and methods for their production have been proposed previously, among which are included several dual-phase steels, such as disclosed, for example, in U.S. Pat. Nos. 3,951,696, 4,033,789, and 4,062,700. However, none of the prior disclosures deal with a predominantly ferrite-martensite material structure which is achieved through the unique combination of chemical composition and heat treating techniques proposed in the present invention.